Sinking \Sink"ing\, a. & n. from {Sink}. {Sinking fund}. See under {Fund}. {Sinking head} (Founding), a riser from which the mold is fed as the casting shrinks. See {Riser}, n., 4. {Sinking pump}, a pump which can be lowered in a well or a mine shaft as the level of the water sinks.